基于阴离子交换反应的NiMn-LDH电极电容性能提升研究

Study on improvement of capacitance performance of NiMn-LDH electrode material by anions exchange

采用一步水热法在泡沫镍网上原位生长镍锰基层状双氢氧化物(Ni Mn-LDH)纳米片阵列电极,并通过氢氧化钾溶液中浸泡的方式提升电极的容量。采用SEM、XRD、TEM和XPS等手段对浸泡前后的电极材料进行表征。结果表明,在浸泡前后Ni Mn-LDH电极的形貌没有变化,但在电极材料内部发生了明显的CO_(3)^(2-)和OH^(-)的交换反应,降低体积较大的CO_(3)^(2-)在LDH层间的分布数量,使层内空间成为OH;的"蓄水池",缩短了电荷存储过程中OH^(-)的迁移距离,因此电容性能有了明显提升。电化学测试结果表明,在5 mA/cm^(2)电流密度下,电极的比电容从18.0 F/g增加至766.6 F/g(1.69 F/cm^(2))。将该电极与活性炭组装的全固态不对称超级电容器在功率密度为900 W/kg时,可呈现的能量密度为35.9 W·h/kg,并且器件的循环稳定性良好。

NiMn-LDH nanosheet arrays on Ni foam were synthesized via one-step hydrothermal method,and the capacitive performance was enhanced by soaking the nanoarrays on KOH solution.The as-obtained electrode before and after the soaking process were characterized by SEM,XRD,TEM and XPS technologies.The results showed that the morphology of NiMn-LDH electrode did not change before and after immersion,but anion exchange reaction between CO_(3)^(2-)and OH;anions was occurred in the electrode materials obviously,which reduced the distribution quantity of large CO_(3)^(2-)between LDH layers,made the space in the layer become the“reservoir”of OH^(-),and reduced the migration distance of OH^(-)in the charge storage process.Therefore,the capacitance performance had been significantly improved.The electrochemical test results showed that the specific capacitance of the electrode increased from 18.0 F/g to 766.6 F/g (1.69 F/cm^(2)) at the current density of 5 mA/cm^(2).When the power density of the all solid-state asymmetric supercapacitor assembled with the electrode and activated carbon was 900 W/kg,the displayed energy density was 35.9 W·h/kg,and the cycle stability of the device was good.